Binocular with improved prism mount

ABSTRACT

A prism binocular with molded hollow body housings each having a preformed shelf or seat to receive a first prism in optical alignment behind an objective lens. The prism is clamped in place by a block which carries a second prism positioned ahead of an ocular lens. The block is secured to the housing interior, and is movable to provide a coarse collimation adjustment during assembly of the binocular. A cover panel is fitted over the front of the housing and includes an integrally formed light shield extending toward the first prism. The ocular lens has a rapidfocus adjustment, and fine collimation is provided by adjustment screws which hold the objective lens in a mounting tube on the cover panel.

United States Patent 1 Akin, Jr. et al.

[111 3,744,872 [451 July 10,1973

[ BINOCULAR WITH IMPROVED PRISM MOUNT [75] Inventors: Alfred A. Akin,Jr., West Covina;

David P. Bushnell, Altadena, both of Calif.

Related US. Application Data [63] Continuation-impart of Ser. No.70,686, Sept. 9,

1970, abandoned.

[52] US. Cl 350/36, 350/51, 350/287 [51] Int. Cl. G02b 21/20, G02b 7/18[58] Field of Search 350/36, 51, 287

[56] References Cited UNITED STATES PATENTS 11/1920 Fujii 350/36 UX4/1925 Harwix 350/287 a. s g

1 ii W. j

//// IIIIIllIllII/lllllll!Illlllllllll Primary Examiner-David H. RubinAttorney-Christie, Parker & Hale 57 ABSTRACT A prism binocular withmolded hollow body housings each having a preformed shelf or seat toreceive a first prism in optical alignment behind an objective lens. Thepn'sm is clamped in place by a block which carries a second prismpositioned ahead of an ocular lens. The block is secured to the housinginterior, and is movable to provide a coarse collimation adjustmentduring assembly of the binocular. A cover panel is fitted over the frontof the housing and includes an integrally formed light shield extendingtoward the first prism. The ocular lens has a rapid-focus adjustment,and fine collimation is provided by adjustment screws which hold theobjective lens in a mounting tube on the cover panel.

6 Claims, 16 Drawing Figures PATENIEUJUL 1 mm 3. 744 87 2 sum 3 BF 3Illlll 1 BINOCULAR WITH IMPROVED PRISM MOUNT CROSS REFERENCE TO RELATEDAPPLICATION This is a continuation-in-part of my co-pending applicationSer. No. 70,686 filed Sept. 9, 1970, now abandoned.

BACKGROUND OF THE INVENTION Prism binoculars have been in use for manyyears, and are typically constructed as a hinged body carrying a pair ofmonocular telescopes which are movable with respect to each other toprovide an interpupillary spacing adjustment. Each monocular has ocularand objective lenses, and a pair of prisms provide a folded optical pathbetween the lenses. The prisms and lenses must be set and maintained inprecise alignment or collimation to prevent eye strain, and to providean accurate image of a scene being viewed. Mounting mechanisms used inthe past for holding the prisms and lenses have been expensive andcomplex to assemble and adjust, and these factors have limited thedevelopment of low-cost prism binoculars having satisfactory opticalquality.

The binocular of this invention uses molded body housings which have apreformed seat for receiving and aligning one of the two prisms in eachmonocular. The other prism is held on a block which is adjustablysupported within the housing to clamp the seated prism in place. Thisconstruction simplifies assembly of the binocular, and provides a ruggedunit which can withstand shock and mishandling without loss of opticalalignment. Each objective lens is carried in a tube integrally formed ona panel which covers the front of the housing, and the ocular lens isheld in a focusing assembly movably mounted on a tube extendingrearwardly from the housing. The binocular is designed to minimizecomponent cost and assembly time, but without sacrificing opticalquality and ruggedness.

' SUMMARY OF THE INVENTION Briefly stated, this invention relates to animproved monocular body assembly for a prism binocular having a pair ofmonoculars each having ocular and objective lenses. First and secondprisms are positioned in an optical path between the lenses, each prismhaving a front face through which light enters and exits, and a pair ofinternally reflecting rear faces.

The improved monocular body includes a hollow housing adapted to supportthe ocular lens, and having on its inner surface an integral hollow bossor forwardly extending wall whichdefines a recessed shoulder forming aprism seat. The rear faces of the first prism have peripheral edgespositioned against and optically aligned by the seat. A mounting blockis secured within the housing, and the block supports the second prismin optical alignment with the first prism and ocular lens. A covermember is secured to the housing to enclose the prisms within thehousing, and to support the objective lens in optical alignment with thefirst prism.

Preferably, the mounting block is positioned over and secured to thehollow boss with the two prisms being disposed on opposite sides of theblock at maximum separation. An adjustment means is provided between themounting block and boss to permit repositioning of the second prism forrough collimation during assembly. The first prism is cushioned againstshock by a resilient pad positioned between the prism and a floor of theboss, and a second resilient pad positioned between the prism andmounting block.

Preferably, the hollow housing includes focus means for movablysupporting the ocular lens, the means having a focus ring which isrotatable to focus the monocular by moving the ocular lens along itsoptical axis. The focus rings of the two monoculars rotate in oppositedirections to move the ocular lenses in the same direction along therespective optical axes. That is, the focus rings are moved in oppositedirections to shift both lenses, for example, from a near-object focusto a distant-object focus. The cover member of the monocular housingincludes a hollow tube in which the objective lens is mounted, and aplurality of angularly spaced alignment screws are threaded through thetube to bear on the objective lens. Lateral shifting of the objectivelens during alignment of the monocular optics is achieved bydifferential adjustment of the screws.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a top view, partly insection, of a binocular according to the invention;

FIG. 2 is a front view, partly broken away, of the binocular;

FIG. 3 is a rear view of the binocular;

FIG. 4 is a front view of a left-hand monocular housing with opticsremoved;

FIG. 5 is a view on line 5-5 of FIG. 4;

FIG. 6 is a view on line 6-6 of FIG. 4;

FIG. 7 is a view on line 7-7 of FIG. 4;

FIG. 8 is a front view of a front cover panel and light shield;

FIG. 9 is a side view, partly in section, of the cover panel shown inFIG. 8;

FIG. 10 is a sectional side elevation on line 10-10 g of FIG. 11, of aprism and prism block;

FIG. 11 is a front view of the prism block with the prism removed;

FIG. 12 is a side view of a Porro prism and associated pads;

FIG. 13 is an end view of the prism;

FIG. 14 is a front view of the prism;

FIG. 15 is an enlarged sectional elevation of a focusing eyepieceassembly; and

FIG. 16 is a view similar to FIG. 1 but restricted to a portion of analternative prism block and monocular housing. I

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT A prism binocular 10 isshown in FIGS. 1-3, and includes a pair of monoculars 11 and 12 havinghinge portions 13 and 14 respectively which are interfitted and securedtogether by a hinge pin 15 held in place by a lock screw 16.Monocularsll and 12 are substantially identical (with the exception of areversal of parts associated with the prisms and other opticalcomponents in the folded optical system of each monocular), and onlymonocular 11 need be described in detail.

Monocular 11 has a hollow housing 18 shown in detail in FIGS. 4-7.Housing 18 has a rear wall 19 with an integrally formed, inwardlystepped ocular tube 20 extending therethrough. A slot 21 (FIG. 5) isformed through a thickened portion of rear-wall 19 adjacent its outeredge to provide an anchor for a neckstrap (not shown).

A continuous sidewall 22 extends forwardly from rear wall 39, andpartially encloses a space 23 in which a pair of prisms are positionedas described below. The front edge of sidewall 22 is recessed to definea shoulder 24.

A generally oval or racetrack-shaped inner wall 26 extends forwardlyfrom rear wall 19, and is integrally formed with the rear wall as wellas with portions of ocular tube 20 and sidewall 22 to define aprism-receiving hollow boss. As shown in FIG. 4, the long axis of ovalinner wall 26 is oriented at approximately 45 to the top surface of themonocular housing.

The inner surface of wall 26 defines a shallow (about 0.8 mm in width)inwardly extending shoulder or shelf 27. As shown in FIGS. 4 and 6-7,shelf 27 is spaced slightly rearwardly of the front edge of wall 26 atits curved ends, and extends rearwardly toward rear wall 19 to a flatportion 28 (FIG. 7) at the center of the straight portion of the innerwall and spaced slightly forward of rear wall 19. Preferably, the innersurface of wall 26 adjacent ocular tube 20 has an inwardly slopingportion 30 (FIG. 7) to strengthen this portion of the structure. Walls19, 22 and 26, and ocular tube 20 are integrally formed so housing 18 isa single molded member.

A conventional upper or first Porro prism 35 (FIGS. 12-14) has agenerally oval-shaped front face 36, and a pair of perpendicularlyoriented rear faces 37 extending at 45 angles to the front face andtoward each other to a flat rectangular base 38. One side of the prismdefines a chamfered portion 39 to provide clearance for sloping portion30 when the prism is installed within inner wall 26 of the monocularhousing.

A first rectangular pad 40 is positioned on base 38 of the prism, and asecond inwardly tapering pad 41 is centrally positioned on front face36.. The pads can be secured to the prism with a drop of cement for easeof handling. The pads are made of a resilient material such as 30-shoreneoprene.

Referring to FIGS. 1, 2 and 6, first prism 35 is positioned within innerwall 26 with the peripheral edges of rear faces 37 and base 38 seatedfirmly against shelf 27 The V-shaped shelf forces the prism into correctalignment as the prism is gently tapped into place. Resilient pad 40 ispositioned between the inner surface of rear wall 19 and base 38 of theprism to protect the prism if the binoculars are dropped or otherwiseabused.

A mounting block 44 is secured over a portion of front face 36 of prism35 (see FIG. 2), and is held in place by screws 45 threaded into matingholes in bosses 46 on the outer surfaces of ocular tube 20 and wall 26.Pins or dowels (not shown) can be provided on block 44 to fit intomating sockets (not shown) in ocular tube 20 or wall 26 to insurecorrect alignment of the block. Pad 41 is compressed between the frontface of prism 35 and the rear surface of block 44 to clamp the prismagainst shelf 27.

Block 44 (FIGS. and 11) is generally oval in planform, and has a pair ofcircular light-passage openings 48 formed therethrough. A web 49 extendsacross the block between the openings. Counterbored clearance holes 50for screws 45 are formed through bosses 51 on the periphery of theblock. The front surface of the block is recessed to define an ovalshoulder 52 which extends around circular openings 48.

A lower or second Porro prism 55 has a front face 56, rear faces 57, anda base 58. This second prism is identical in geometry to first prism 35but can be slightly smaller in size as the conical bundle of light rayspassing through the optical system decreases in diameter between thefirst and second prisms. Second prism is positioned on block 44 with theperiphery of front face 56 seated against oval shoulder 52 of the block.The prism is secured in place by a U-shaped metal (phosphor bronze)clamp 60 which is urged against base 58 of the prism and secured inplace by screws 61 threaded into the block.

Prisms 35 and 55 are spaced apart by block 44 as far as possible withinthe confines of housing 18. The rearward location of prism 35 andforward location of prism 55 positions these components in relativelynarrow (as compared to conventional binoculars in which the prisms aremounted face to face) regions of the conical bundle of light rayspassing through the instrument. The prisms can therefore be smaller andlighter than corresponding prisms used in conventional de- SlgllS.

A front panel 65 (FIGS. 1 and 8-9) extends across the front of sidewall22 to enclose housing 18. Panel 65 is fitted against shoulder 24 of thehousing sidewall, and is cemented in place. Alternatively, these partscan be bonded to each other using ultrasonic-welding techniques. Acircular opening 66 extends through panel 65, and an objective-lensmounting tube 67 extends around the hole and forwardly from the panel.An annular groove 68 is formed in the panel at the base of tube 67, anda second peripheral groove 69 extends around tube 67 adjacent itsforward end. Four threaded openings 70 extend through the wall of themounting tube, and these openings are evenly spaced 90 apart around thetube.

A conventional objective lens 74 (FIG. 1) is positioned within mountingtube 67 against an O-ring 75 seated in groove 68. An externally threadedlocking ring 76 is threaded into internal threads formed on the innersurface of tube 67 to lock the objective lens in place. A thin metalband 77 of a material such as soft aluminum extends around the edge ofthe objective lens, and set screws 78 are threaded through openings 70in the mounting tube to bear against band 77. The lens can be shiftedlaterally during collimation of the monocular by adjusting set screws78.

A circular cap 80 (FIG. 1) has a central opening 81 in front of theobjective lens, and is fitted over mounting tube 67. The cap has aninwardly extending annular rib 82 which fits into groove 69 to hold thecap on the tube. Cap 80 is made of a flexible material such as neoprenewhich can be slightly deformed when rib 82 is forced over the front ofthe mounting tube during installation of the cap.

A generally conical light shield 84 is integral with front panel 65 andextends rearwardly from the panel around opening 66. A portion of thelight shield is cut away to define a stepped notch 85 which provides aclearance space for mounting block 44 as shown in FIG. 1. The innersurface of the light shield is black in color, and it prevents strayreflections within the housing which could interfere with image quality.

A focusing eyepiece assembly 88 is rotatably mounted on ocular tube 20as best seen in FIG. 15. The assembly includes a tubular lens cell 89making a slip fit within tube 20. Cell 89 is reduced in outside diameter adjacent its rear end to define an annular shoulder 90, and theinner surface of the cell defines a pair of annular shoulders 91 and 92on opposite sides of shoulder 90. An O-ring seal 93 is seated in anannular groove in the outer surface of the cell adjacent its forwardend, and the seal prevents entry of dust or moisture into the monocularhousing interior.

A conventional compound ocular lens 95 is seated within cell 89 againsta gasket 96 on shoulder 91. A field lens 97 is air-spaced forwardly oflens 95 by an annular spacer 98 having an inwardly turned lip 99 at itsrear end which bears on and clamps lens 95 against gasket 96. Aretaining ring 100 is threaded into the forward end of lens cell 89 tosecure the field lens against the spacer.

A focus ring 103 fits loosely over ocular tube 20, and is reduced indiameter at its rear end to define a circular portion 104 fitted snuglyover the end of cell 89 to abut shoulder 90. The focus ring is rigidlysecured to cell 89 by four pointed set screws 105 threaded into andspaced evenly around the ring to extend into shallow sockets in thecell. An annular groove 106 in the outer surface of portion 104 providesa seat for an inwardly extending retaining rib 107 on an annular eyecup108 extending from the rear end of the focus ring. The eyecup is made ofan elastomer such as neoprene which will stretch sufficiently for rib107 to pass over the end of the focus ring and seat in groove 106.

A pair of cam slots 110 are formed on opposite sides of and partiallythrough the wall of cell 89. A pair of guide pins 111 are threaded intothe cell to mate with cam slots 110. Each cam slot extends about 90around the lens cell, and the slots are sufficiently steep that theocular lens is moved along its axis through a full focusing range (forboth near and distant objects) within the length of the cam slots as thefocus ring is rotated about 90 or less. This style of fast-focusingmechanism is further described in US. Pat. No. 3,540,792.

A knurled focusing knob 112 (FIG. 3) is formed on the surface of focusring 103, and a pointer 113 on the focus ring indicates focus positionof the ocular ring with respect to distance-scale markings 114 on rearwall 19 of the monocular housing. Preferably, the focusing cam slots onmonoculars l1 and 12 are oppositely oriented so the ocular lenses aredriven in the same direction along their parallel optical axes byopposite rotation of the respective focus rings. This has been found tobe an effective and natural way of achieving rapid and accurate focus ofthe two monoculars, and knobs 112 are positioned to fall under theuser's thumbs when the binoculars are held normally so a shift in handposition is not required during refocusing.

Housing 18, mounting block 44, front panel 65, lens cell 89 and focusring 103 are preferably each integrally molded from a plastic materialsuch as ABS (acrylonitrile, butadiene and styrene) resin with about 40-percent glass fibers as a filler. This material is lightweight andstrong, and provides a finished product with an attractive appearance.

The alignment latitude afforded by set screws 78 which shift theobjective lens is a relatively fine adjustment, and it may be desirableto provide a second coarse collimation adjustment to permit roughoptical alignment during assembly of the various components. This ismost easily achieved by incorporating an adjustment means for shiftingthe position of mounting block 44 so second prism 55 can be tippedslightly for rough alignment before the front panel and objective lensare secured in place.

One form of a suitable coarse adjustment is shown in FIGS. 1, 2, 4 andS. An additional pair of bosses are formed on ocular tube 20 inalignment with a matching pair of bosses 121 on mounting block 44. Apair of self-tapping screws 122 are threaded into holes in bosses 120,and the heads of the screws fit into recesses 123 in the undersurface ofbosses 121. A smalldiameter hole 124 is drilled through each boss 121into recess 123 so the heads of screws 122 can be rotated with a smallscrewdriver (not shown).

If any significant prism misalignment is noted during assembly, eitheror both of screws 122 is rotated to back the screw head slightly awayfrom boss 120 and against mounting block 44 to space the block slightlyaway from the ocular tube. Tipping of prism 55 along its long axisresults from equal adjustment of screws 122, and tipping along the shortor lateral axis of the prism is achieved by differential adjustment ofthe screws. Screws 45 are tightened to secure the mounting block oncethe desired coarse alignment is achieved, and final post-assemblycollimation is done by adjusting the objective lens with setscrews 78.

An alternative arrangement is shown in FIG. 16 where the holes in bosses120 are omitted, and a slotted-head set-screw 127 is threaded into holes128 in each of bosses 121. An enlarged pad 129 is formed on the innerend of each setscrew 127, and the pad seats in a clearance recess 130 atthe inner end of hole 128. Advancing rotation of either setscrew forcesthe setscrew pad against the top of facing boss 120 to space themounting block away from the ocular tube. Uniform or differentialadjustment of the setscrews is made until the desired coarse prismalignment is achieved. The components are locked in place by tighteningscrews 45, and the alignment is preserved by locking setscrews againstfurther movement with a drop of cement.

Conventional setscrews (not shown) can also be used instead of pad-endsetscrews 127, but it is then desirable to put a metal insert in facingboss 120 to distribute the load across the boss and keep the narrow endof the setscrew from digging into the plastic material which forms boss120. Whichever arrangement is selected, the screws are in effect actingas adjustable spacers to permit quick coarse adjustment of prism 55 asan inital step in collimating the binocular optics.

There has been described a low-cost prism binocular which is madeprimarily of inexpensive, lightweight moleded-plastic parts which can beassembled by relatively unskilled workers. The binocular issubstantially sealed and will float if accidentally dropped in water.Elimination of conventional prism-mounting mechanisms providessimplified assembly and improved resistance to shock forces which mightbreak or misalign the prisms of conventional designs.

What is claimed is:

1. In a prism binocular having a pair of monoculars each includingocular and objective lenses, and first and second prisms positioned inan optical path between the lenses; each prism having a front facethrough which light enters and exits, and a pair of rear faces, animproved monocular body assembly for each monocular comprising:

a hollow housing adapted to support the ocular lens and having on itsinner surface an integral hollow boss forming a recessed prism seat, therear faces of the first prism having peripheral edges positioned againstand aligned by the seat;

a mounting block secured within the housing and adapted to receive andsupport the second prism in optical alignment with the first prism andthe ocular lens;

adjustment means in contact with the mounting block and arranged toprovide an adjustable separation of the mounting block and hollow bossso the position of the second prism can be varied during opticalalignment of the monocular; and

a cover member secured to the housing to enclose the prisms within thehousing, the cover member being adapted to support the objective lens inoptical alignment with the first prism.

2. The improvement defined in claim 1 in which the mounting block ispositioned over and secured to the hollow boss, the prisms beingdisposed on opposite sides of the block.

3. The improvement defined in claim 2 and further comprising a resilientpad disposed between the first prism and the boss, and a secondresilient pad disposed between the first prism and mounting block.

4. The improvement defined in claim 1 in which the hollow housingincludes focus means for movably supporting the ocular lens, the focusmeans having a focus ring which is rotatable to focus the monocular bymoving the ocular lens along its optical axis, the focus rings of thetwo monoculars being arranged to rotate in opposite directions to movethe ocular lenses in the same direction along the respective opticalaxes.

5. The improvement defined in claim 4 in which the mounting block ispositioned over and secured to the hollow boss, the prisms beingpositioned on opposite sides of the block, and further comprising aresilient pad disposed between the first prism and the boss, and asecond resilient pad disposed between the first prism and mountingblock.

6. The improvement defined in claim 5 in which the adjustment meanscomprises a pair of screws disposed between and arranged for adjustableseparation of the block and boss so relative position of the prisms isadjustable.

mg UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No.3,744,872 Dated y 1973 Alfred A. Akin, Jr. and David. I. BushnellInventor(s) It is certified that error appears in the above-identifiedpatent and that said Letters Patent are hereby corrected as shown below:

On the cover sheet, item 73 "Bushnell Optical Company, Pasadena,California" should read --Bausoh & L b Incorporated, Rochester, NewYork-- Signed and sealed this 27th day of November 1973.

(SEAL) Attest: v Q

' ETCHE R JR. RENE n. TEGT'MEIER l i c i s c i l i5 6fficer ActingCDIIIIIIZLSSlOIlGT of Patent:

my UNITED STATES PATENT OFFICE CERTIFICATE OF QGHRECTION 3,744,872 DatedJuly 10, 1973 Patent NO.

Alfred A. Akin, Jr. and David P. Bushnell Inventor(s) It is certifiedthat error appears in the above-identified patent and that said LettersPatent are hereby corrected as shown below:

item 73 "Bushnell Optical Company,

On the cover sheet, Pasadena, California" should read --Bausch 8: LombIncorporated, Rochester, New York-- Signed and sealed this 27th day ofNovember 1973.

(SEAL) Attest:

I ER JR. RENE n. TEGTMEYEP: I EDWARD M'FLETCH Acting Commissioner ofPatents Attesting Offi

1. In a prism binocular having a pair of monoculars each includingocular and objective lenses, and first and second prisms positioned inan optical path between the lenses; each prism having a front facethrough which light enters and exits, and a pair of rear faces, animproved monocular body assembly for each monocular comprising: a hollowhousing adapted to support the ocular lens and having on its innersurface an integral hollow boss forming a recessed prism seat, the rearfaces of the first prism having peripheral edges positioned against andaligned by the seat; a mounting block secured within the housing andadapted to receive and support the second prism in optical alignmentwith the first prism and the ocular lens; adjustment means in contactwith the mounting block and arranged to provide an adjustable separationof the mounting block and hollow boss so the position of the secondprism can be varied during optical alignment of the monocular; and acover member secured to the housing to enclose the prisms within thehousing, the cover member being adapted to support the objective lens inoptical alignment with the first prism.
 2. The improvement defined inclaim 1 in which the mounting block is positioned over and secured tothe hollow boss, the prisms being disposed on opposite sides of theblock.
 3. The improvement defined in claim 2 and further comprising aresilient pad disposed between the first prism and the boss, and asecond resilient pad disposed between the first prism and mountingblock.
 4. The improvement defined in claim 1 in which the hollow housingincludes focus means for movably supporting the ocular lens, the focusmeans having a focus ring which is rotatable to focus the monocular bymoving the ocular lens along its optical axis, the focus rings of thetwo monoculars being arranged to rotate in opposite directions to movethe ocular lenses in the same direction along the respective opticalaxes.
 5. The improvement defined in claim 4 in which the mounting blockis positioned over and secured to the hollow boss, the prisms beingpositioned on opposite sides of the block, and further comprising aresilient pad disposed between the first prism and the boss, and asecond resilient pad disposed between the first prism and mountingblock.
 6. The improvement defined in claim 5 in which the adjustmentmeans comprises a pair of screws disposed between and arranged foradjustable separation of the block and boss so relative position of theprisms is adjustable.